Within the past five years, the importance of sexual transmission of enteric pathogens has been increasingly recognized in the sexually active male homosexual population. As a result, infectious proctitis-enteritis has become more common in homosexual men. However, fewer than 40% of the cases result from gonococcal infection and the etiology of the remaining cases and the question of mixed infection is still undefined. In this proposed study we plan the following: 1) Use specialized microbiologic techniques in a case control prospective study to ascertain the association of selected pathogens with the enteritis-proctitis syndrome in homosexual men. 2) Describe the histopathology and clinical features of proctitis and/or enteritis due to each pathogen. 3) Characterize the effectiveness of specific therapy in cases in which pathogens are identified and of tetracycline in cases in which no pathogen is identified. 4) Evaluate the epidemiology of proctitis and enteritis in homosexual men, and assess the modes and risk of transmission.